Proteolipids can be extracted from bovine heart tissue with chloroform-methanol (2:1, v/v) and subsequently delipidated by dialysis. The most abundant heart apoprotein was prepared in pure form by a combination of gel filtration chromatography and preparative gel electrophoresis on 0.1% sodium dodecyl sulfate. The molecular weight of the apoprotein is 30,500 plus or minus 600 daltons. During the coming year an amino acid sequence determination of the most abundant heart apoprotein will be undertaken. Since the hydrophobic apoprotein is highly aggregated in water, detergents will be used to solubilize the protein during tryptic digestion. CNBr will also be used to chemically cleave the protein. Peptides will be purified by gel filtration chromatography and ion-exchange chromatography or by high voltage paper electrophoresis. It is anticipated that a few peptides will be obtained in sufficient amounts to allow partial sequence determination by the Edman degradation procedure. It is of interest to establish the subcellular location of proteolipids that are prepared from whole tissue extracts. Thus proteolipid apoproteins from rat liver tissue and rat liver mitochondria will be prepared. The polyacrylamide gel electrophoresis patterns of mitochondria proteolipids will be compared with proteolipids found in whole tissue extracts in order to establish whether a common set of proteolipids are present in both preparations.